An evolutionary scandal

"Clonality" by John C Avise is a scientific, scholarly overview of clonal and asexual reproduction among vertebrates. The book is rather technical, and hence not suited for the general reader. Here's a sample sentence: "One likely hypothesis is that this outcome arose by a form of automixis, or automictic parthenogenesis, wherein mitotic-type divisions follow a meiotic reduction division and yield multiple haploid cells, some of which are genetically identical." If you're currently taking advanced biology classes, this is the book for you!

As a layperson, I could only skim the book. But yes, it does contain some pretty weird information. The phenomenon of "virgin birth" or parthenogenesis is usually associated with invertebrates (aphids come to mind), but also occurs in certain species of lizards. There is even a "lesbian" lizard which engages in pseudo-copulations, despite procreating by parthenogenesis. Since all offspring are clones of the mother, parthenogenetic species of this kind are usually all-female. Interestingly, parthenogenesis occasionally occurs even among sexually reproducing species. For instance, some turkeys and other game birds have occasionally propagated by "virgin birth" from unfertilized eggs.

Even more bizarre are the phenomena known as gynogenesis and hybridogenesis. (I never understood a third version, known as kleptogenesis!) Gynogenesis means that a parthenogenetic female of one species mates with a male from another species, but the sperms don't really fertilize the female egg. They trigger the development of the embryo, but no more. In essence, the foreign male is sexually parasitized by the "virgin" female (a feminist dream?). Hybridogenesis is more complex: the male becomes the biological father of the hybrid offspring, but is prevented from becoming the biological grandfather of the next generation, since the hybrid casts off his genetic material before reproducing. A frog thing, apparently.

The book also discusses identical quadruplets among armadillos, hermaphroditic fish, and (of course) Dolly and the vexing question of human cloning. There are also sections dealing with the evolutionary pros and cons of asexual reproduction. The author believes that parthenogenesis is a derived trait, and that it's somehow evolutionary unstable in the long run. He admits, however, that some invertebrates that reproduce asexually might be very ancient (tens of millions of years old) and calls this "an evolutionary scandal". The scandalous creatures are known as darwinulid ostracods, bdelloid rotifers and orbatid mites. Creative evolution?

"Clonality" is probably a five-star book, but since I'm not an expert on the issues under debate, I give it four. Somebody should write a more popularized version of this book!